The effects of afferent feedback in a brain-computer interface (BCI) system in a healthy population

A summary of two subprojects Both subprojects have a different number of sessions. In the first subproject, there are three sessions. For subproject 2, there are two sessions. a)In Subproject 1, we will Investigate the effect of the type of sensory feedback that a patient receives from assistive technologies (functional electrical stimulation and mechanical robot stimulation) on the communication between the brain and muscles. In this subproject, functional electrical stimulation, mechanical stimulation and joint electrical and mechanical stimulations will be triggered in three separate experimental sessions with at least 24 hours gap. The neuroplastic changes in the nervous system (communication between the brain and muscles) will be quantified by taking the difference between the cerebral and muscular activation before and after each experimental session using TMS. Although this subproject will be evaluated with healthy volunteers, the prospect is to apply the optimal (regarding induction of plasticity) type of sensory feedback in stroke patients with motor impairments. b)In Subproject 2, we will compare techniques for assessing the communication between the brain and muscles and how they relate to each other. This will be performed in two experimental sessions where coherence measures are recorded pre- and post-intervention in one session and TMS is used pre- and post-intervention in the other session to quantify potential changes with at least 24 hours gap. This project will thus compare the outcome of coherence measures with TMS (gold standard). We hypothesize that coherence will effectively assess neuroplastic changes after BCI intervention. In this scenario, it would be possible to assess the effect of rehabilitation without any risk or discomfort for the patient, and the evaluation could potentially be performed to give the clinicians and patients an indication of the progress/effect of the training. Moreover, this could also improve further research within the area of rehabilitation of stroke patients. BCI intervention: a single electrical/mechanical stimulation of the common peroneal nerve or tibial nerve will be delivered in conjunction with a variety of motor tasks (they will be asked to imagine or execute the feeling of a lower limb muscle contracting) or a movement task. Following measures will be used to investigate the hypotheses that are the focus of this project a). Transcranial Magnetic Stimulation (TMS): TMS involves magnetic stimulation of areas of the brain that control motor activity and pathways. This allows us to gauge the state of the excitability of the pathways involved. It has been routinely used in neurophysiological research studies for the past 20 years and is also used in clinical practice. A TMS assessment involves applying consistent magnetic stimuli to the brain and recording EMG activity from the targeted muscle. The level of activity in the muscle will change based on the level of excitability in the nervous system. We will assess whether the level of excitability changes pre and post the different interventions that we will be applying based on the EMG recordings of the target muscle. TMS is considered to be safe when proper guidelines and safety checklists are adhered to. We will be following standard best practice procedures when making TMS recordings and will be using the safety checklist. For quantification of cortical excitability, 15 stimuli with 120% of the motor threshold will be delivered to participants pre, post and post30 minutes for three sessions of subproject 1 and session 1 of Subproject2. TMS will be administered by pacing the TMS coil over the motor cortex to deliver the TMS magnetic pulse by trained staff. PI of the application has experience of using TMS for around ten years. Other team members have varying length of experience of administering the TMS in research setup ranging from 1- 5 years. b)Evoked potentials (EP)/EEG: Evoked potentials (EPs) rely on recording brain activity (using EEG) in combination with a task, in this case, dorsiflexion of the foot. In particular, different electrical potentials occur at different times in the brain depending on what tasks, pathways and recording sites are involved. The electrical strength of these peaks can vary based on brain activity. All evoked potential recording electrodes will be placed according to the International Federation of Clinical Neurophysiologists (IFCN) recommendations and our own experience or others in the literature. c)surface EMG : Surface EMG will be used to record muscle activity in the lower limb tibialis anterior (TA) when the participant is performing motor tasks (holding a small contraction). Surface EMG will be recorded by placing an electrode over the TA muscle using standard EMG placement and recording techniques. There are no safety issues associated with recording surface EMG. Participant Involvement: For all the sessions in subproject 1 and 2, we need time commitment from participants. They will be asked to perform ankle movements while EEG and EMG activity being recorded. EEG activity during ankle movement intention will be utilized to activate one of the three methods,1) electrical stimulation of the common peroneal nerve,2) mechanical stimulation and 3) combination of 1 and 2 for subproject ones three sessions. TMS at 120 % of the resting threshold will be used to assess the corticomotor excitability at pre, post and post 30 minutes after the intervention in 3 sessions of subproject 1. During two sessions of the subproject 2 (which will start once subproject one is finished) best feedback mode decided in subproject one will be used, but for assessment in TMS and EMG-EEG coherence in separate sessions at pre, post and post 30 minutes after the intervention. Throughout the project, the random sample of subjects will be interviewed to see what happened in the session to monitor the adherence and fidelity to the intervention.